Commitments, Off-Balance Sheet Arrangements, and Legal Proceedings (Residential Mortgage Repurchase Reserve) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Summary of changes in the residential mortgage repurchase reserve [Line Items]
Loans Repurchased Under Make Whole Requests	$ 126,000	$ 3,000,000
Residential mortgage repurchase reserve
Balance at beginning of year	24,000,000
Balance at end of year	24,000,000	24,000,000
Loss Reimbursement Claims Under Make Whole Requests	3,000	133,000
Loans Sold To Outside Investors Original Amount	7,900,000,000
Loans Sold To Outside Investors Remaining Outstanding Amount	5,700,000,000
Mortgage Repurchase Reserve [Member]
Residential mortgage repurchase reserve
Balance at beginning of year	1,197,000	3,258,000
Repurchase provision expense	70,000	428,000
Adjustments to provision expense	0	(2,450,000)
Charge offs, net	(3,000)	(39,000)
Balance at end of year	$ 1,264,000	$ 1,197,000